Question

Describe and label the regions on the lac operon. Include the following: regulatory gene, promoter region, operator, structural genes, and repressor. What happens in the presence of glucose? Lactose?

Answer 1

Lac Operon is lactose Operon. It is a set of structural genes which are regulated by a common promoter.

Promoter is the DNA sequence on Lac Operon where RNA polymerase bind and initiate the transcription of genes which are located downstream to it.

After the promoter is present DNA sequence called operator. This operator is the regulatory region of the Lac Operon. When lactose Operon is not actively transcribing, a proteinaceous molecule called lactose repressor binds to operator and prevents RNA polymerase from transcribing the Operon.

There are three structural gene in lactose Operon. These are called as Lac z, y and a. Lac Z codes for beta galactosidase. This enzyme cleaves lactose into galactose and glucose molecules inside the bacterial cell. Lac Y codes for permease. This enzyme is responsible for uptake of lactose from the medium inside the cell. Lac A codes for transacetylase enzyme. The function of this enzyme is not yet cleared.

Whenever glucose is present in the medium then lactose Operon is switched off. In this condition repressor is present on the operator and prevents RNA polymerase from transcribing the operon.

But when lactose is present in the medium then the lactose molecules bind with the repressor present on operator and degrade it. Due to this the RNA polymerase is able to transcribe the Operon and therefore transcription of all the structural genes occur and the proteins are also made from those genes.

Please rate.